An irrigation system is used to dispense water to an area of land containing a lawn or garden. The system usually includes a manifold from which extends a network of pipes terminated by sprinkler heads distributed over the land area being irrigated. The manifold and pipe network are usually located under the ground surface and the sprinkler heads are often of the pop-up type which project above the ground surface when the system is in use.
The manifold is invariably connected to a source of water located inside a building adjacent to the land being irrigated. The connection usually includes a faucet-like valve having an elongated housing which extends through a foundation wall of the building, the head of the faucet and the faucet handle being located at the outside surface of the wall. A faucet stem or shaft extends from the faucet head along the housing to a valve member which is arranged to seal against a valve seat located at the opposite end of the valve housing inside the building. A pipe connects the water supply or mains to the valve inlet located upstream from the valve seat. The valve outlet, located downstream from the valve seat in the valve head is connected by suitable pipes and fittings to the manifold of the irrigation system. Invariably, also, a backflow preventer is included in the line between the valve and the manifold to prevent water in the irrigation system from draining back into the building in the event of a loss of water supply pressure.
The conventional irrigation system is turned on and off, beginning at the start of the growing season, by opening and closing the valve using the valve handle. At the end of the season before the onset of winter, water is usually drained from the irrigation system through a normally closed drain hole located in the valve head. This is done while the valve is closed. To assure that substantially all of the water is purged from the system, air under pressure may be blown into the system through the drain hole causing any water to leave the system through the sprinkler heads. This draining/purging operation also removes all water from the interior of the valve downstream from the valve seat which, as noted above, is located inside the building. In other words, all parts of the valve that are likely to be exposed to cold weather are devoid of water.
Existing shut-off valves of this general type are disadvantaged in many respects. Some such valves provide restrictive flow paths for the water so that there is an appreciable pressure drop across the valve. Whereas water may be delivered to the valve under a typical main pressure of, say, 40 PSI, the water pressure leaving the valve may be only 32 PSI, which pressure may be insufficient to extend the pop-up type sprinkler heads, particularly those at the ends of relatively long pipe runs.
Prior irrigation shut-off valves also tend to be relatively complex and costly structures composed of several different parts which are difficult to make and to assemble. Such complexity also makes it more difficult to inspect and service the prior valves.